84 CHEMICAL EXAMINATION, ETC. 



CHEMISTEY. 



No. 14; the average of 16 specimens is 79.11 

 per cent, of juice in the grape. Dr. Jackson, 

 in 1859, gives an average percentage of juice, 

 in 38 specimens of native grapes, of 67.23. 



" Comparing these with the results which we 

 have for foreign grapes, we find that Berthier 

 determined the percentage of juice in Chasselas 

 and Pineau, grown in the neighborhood of 

 Paris, at 73.81 and 72.43, respectively, or, 

 mean, 73.12. The mean of Dr. Jackson's and 

 of my results is 73.17, which is almost exactly 

 the mean of Berthier's analyses. The amount 

 of juice, therefore, of American grapes is not 

 different from that of the European fruit. 



Chemical Analyses of Grapes. 



" It is very different with respect to the sugar 

 which gives the alcoholic value to the grape. 

 The average percentage of sugar found by me 

 is 12.5; the mean of Dr. Jackson's analysis is 

 11.6 per cent., or, for our examinations com- 

 bined, a mean of 12 per cent., which could not 

 give a wine of greater than 6 per cent, of alco- 

 holic strength. The sugar in the several grapes 

 of the present research varies 7.73 to 20.36 per 

 cent. I found a larger amount of sugar in the 

 tipper than in the lower half of the same 

 bunch of No. 14. The European wine-grapes 

 give a much larger amount of sugar than those 

 which I have analyzed, as may be seen by the 

 table from Mulder, in next column. 



" This is equivalent to a general mean of 19.5 

 per cent, of sugar for all of the grapes ana- 

 lyzed. "We have, therefore, to improve our 

 grapes to the extent of 7 per cent, in sugar be- 

 fore we can make a wine of the same average 

 strength as the European wines. The result is 

 deduced from the consideration of all the 



* Not determined. 



grapes analyzed. If we take certain varieties 

 we will need to improve their sugar to a less 

 degree ; thus the Delaware No. 17 is already a 

 good wine-grape, and No. 2, Baldwin Le Noir, 

 contains an amount of sugar equal to that of 

 European grapes, at least in the specimens 

 analyzed by me, and grown by the Agricul- 

 tural Department. The grape No. 9 is a 

 foreign specimen, having been imported from 

 Sans-Souci, near Berlin, by Mr. C. J. Uhlmarm, 

 in 1860. 



" The amount of acid in the grape-juice de- 

 termines the acidity of the wine, so far as it 

 is not masked by sugar remaining unfermented. 

 Fresenius and others have given analyses of 

 grape-juice in which the tartaric acid varies 

 from 0.56 to 1.11 per cent.; the acid being 

 present as bitartrate of potash. The celebrated 

 Johannisberg grape, of the vintage of 1860, 

 contained 0.74 of tartaric acid, and not more 

 than 19.2 per cent, of sugar, although the same 

 chemist found in the grapes of the Ehinegau 

 from 24 to 28 per cent, of saccharine matter. 



" The results of my examination of American 

 grapes give from 0.80 to 1.75 per cent, of free 

 acid. This is considerably greater than in the 

 analyses above quoted, in which only half the 

 tartaric acid given is free to exert its acid 

 reaction, the remainder being masked by its 

 combination with the potash. Taking both 

 sugar and acid in question, as well as the 

 amount of juice yielded, the specimen, No. 2, 

 is found to be the best wine-grape of those 

 analyzed by me. It remains for a full exami- 

 nation to show in what respect this opinion 

 may have to be modified." 



CHEMISTEY. The Atomic Theory. The 

 most important contribution to literature upon 

 the puzzling question of atoms, or molecules, 

 during the year, is a paper by Sir William 

 Thomson, F. E. S., which appeared in Nature of 

 March 31st, on the size of atoms. That distin- 

 guished investigator opens the discussion by 

 remarking that the idea of an atom has been 

 so constantly associated with assumptions of 

 infinite indivisibility that many naturalists have 

 dismissed it to the realms of metaphysics, and 

 made the atom " smaller than any thing we 

 can conceive." But, if atoms are inconceiva- 

 bly small, why are not all chemical actions in- 

 finitely swift ? as they are not. He then pro- 

 ceeds to defend Cauchy's proposition, made 

 more than thirty years ago, setting forth that 

 the familiar prismatic colors proved the 

 " sphere of sensible molecular action " in 

 transparent liquids and solids to be conforma- 



